U.S. patent number 7,911,758 [Application Number 12/119,546] was granted by the patent office on 2011-03-22 for low power solenoid control system and method.
This patent grant is currently assigned to Automatic Switch Company. Invention is credited to John J. Haller.
United States Patent |
7,911,758 |
Haller |
March 22, 2011 |
Low power solenoid control system and method
Abstract
A low power solenoid control circuit including a power source in
series with a sensing element and a first diode, an inductor to
actuate a valve, an energy storage device to store and discharge
energy into the inductor, diodes to control current flow, and
switches and a controller to control the circuit. The circuit may
be operated by closing a first switch, thereby allowing a source
current to flow through an inductor; opening the first switch,
thereby forcing a charge current to flow through an energy storage
device utilizing the inductance of the inductor; repeating these
steps until the energy storage device is sufficiently charged; and
upon command, closing a second switch, thereby forcing a discharge
current to flow from the energy storage device to the inductor
causing the inductor to produce an actuating magnetic field thereby
actuating a mechanical valve.
Inventors: |
Haller; John J. (Boonton,
NJ) |
Assignee: |
Automatic Switch Company
(Florham Park, NJ)
|
Family
ID: |
40693451 |
Appl.
No.: |
12/119,546 |
Filed: |
May 13, 2008 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20090284891 A1 |
Nov 19, 2009 |
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Current U.S.
Class: |
361/189;
361/93.7; 361/93.1 |
Current CPC
Class: |
H02M
3/155 (20130101) |
Current International
Class: |
H01H
9/00 (20060101); H01H 47/00 (20060101); H02H
3/08 (20060101); H02H 9/02 (20060101) |
Field of
Search: |
;361/160,189 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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19701471 |
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Jul 1998 |
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DE |
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19808780 |
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Sep 1999 |
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DE |
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2779287 |
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Dec 1999 |
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FR |
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2005014992 |
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Feb 2005 |
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WO |
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2005093239 |
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Oct 2005 |
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WO |
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Other References
Michael Lund, International Search Report for International Patent
Application No. PCT/US2009/038118, European Patent Office, dated
Jun. 18, 2009. cited by other .
Michael Lund, Written Opinion for International Patent Application
No. PCT/US2009/038118, European Patent Office, dated Jun. 18, 2009.
cited by other.
|
Primary Examiner: Patel; Dharti H
Attorney, Agent or Firm: Locke Lord Bissell & Liddell
LLP
Claims
What is claimed is:
1. A method comprising the steps of: (a) closing a single first
switch, thereby allowing a source current to flow through an
inductor; (b) opening the single first switch, thereby forcing a
charge current to flow through an energy storage device utilizing
the inductance of the inductor; (c) repeating steps a and b until
the energy storage device is sufficiently charged, wherein steps a
and b are performed a predetermined number of times and the
predetermined number of times is determined through a calibration
process performed upon circuit assembly during manufacturing; (d)
upon command, closing a second switch, thereby forcing a discharge
current to flow from the energy storage device to the inductor
causing the inductor to produce an actuating magnetic field thereby
actuating a mechanical valve.
2. The method of claim 1, wherein the source current is
insufficient to actuate the valve.
3. The method of claim 1, wherein step a is maintained until the
source current reaches a first predetermined level as measured
through a current sensing element.
4. The method of claim 3, wherein step b is maintained until the
source current reaches a second predetermined level as measured
through the current sensing element.
5. The method of claim 1, wherein the calibration process accounts
for both component tolerances and ambient temperature.
6. The method of claim 1, wherein steps a and b are performed with
the second switch open.
7. The method of claim 1, further including the steps of: (e) after
the valve has been actuated, monitoring the source current through
a current sensing element; and (f) once the source current reaches
a predetermined level, repeating steps a and b to recharge the
energy storage device.
8. The method of claim 1, wherein the first switch is a normally
closed depletion mode MOSFET.
9. The method of claim 1, wherein the first SPST switch is a
normally closed depletion mode MOSFET.
10. The method of claim 1, wherein steps a, b, and c further
comprise: maintaining the first SPST switch closed until the source
current rises to a first predetermined level; opening the first
SPST switch when the source current rises to the first
predetermined level; and closing the first SPST switch once the
source current falls to a second predetermined level.
11. A method comprising the steps of: (a) opening a first single
pole single throw (SPST) switch and closing a second SPST switch,
thereby forward biasing a first diode, allowing a source current to
flow through a capacitor charging the capacitor; (b) opening the
second SPST switch, thereby reverse biasing a second diode and
maintaining the charge of the capacitor; (c) closing the first SPST
switch, thereby allowing the source current to flow through a
solenoid coil; (d) opening the first SPST switch, thereby forward
biasing the second diode and forcing a charge current to flow
through the capacitor utilizing the inductance of the solenoid
coil; (e) repeating steps c and d until the capacitor is
sufficiently charged; (f) upon command, closing both the first and
second SPST switches, thereby reverse biasing both the first and
second diodes and forcing a discharge current to flow from the
capacitor to the solenoid coil causing the solenoid coil to produce
an actuating magnetic field thereby actuating a mechanical valve,
wherein step c is maintained until the source current reaches a
first predetermined level as measured through a current sensing
element.
12. The method of claim 11, wherein the source current is
insufficient to produce the actuating magnetic field to the actuate
the valve.
13. The method of claim 11, wherein step d is maintained until the
source current reaches a second predetermined level as measured
through the current sensing element.
14. The method of claim 11, wherein steps c and d are performed a
predetermined number of times.
15. The method of claim 14, the predetermined number of times is
determined through a calibration process and accounts for both
component tolerances and ambient temperature.
16. The method of claim 11, wherein steps c and d are performed
with the second SPST switch open.
17. The method of claim 11, further including the steps of: (g)
after the valve has been actuated, monitoring the source current
through a current sensing element; and (h) once the source current
reaches a predetermined level, repeating steps a and b to recharge
the energy storage device.
18. The method of claim 11, wherein steps a, b, c, d, and e further
comprise: maintaining the first SPST switch closed until the source
current rises to a first predetermined level; opening the first
SPST switch when the source current rises to the first
predetermined level; and closing the first SPST switch once the
source current falls to a second predetermined level.
19. A method comprising the steps of: (a) opening a first single
pole single throw (SPST) switch and closing a second SPST switch,
thereby forward biasing a first diode, allowing a source current to
flow through a capacitor charging the capacitor; (b) opening the
second SPST switch, thereby reverse biasing a second diode and
maintaining the charge of the capacitor; (c) closing the first SPST
switch, thereby allowing the source current to flow through a
solenoid coil; (d) opening the first SPST switch, thereby forward
biasing the second diode and forcing a charge current to flow
through the capacitor utilizing the inductance of the solenoid
coil; (e) repeating steps c and d until the capacitor is
sufficiently charged; (f) upon command, closing both the first and
second SPST switches, thereby reverse biasing both the first and
second diodes and forcing a discharge current to flow from the
capacitor to the solenoid coil causing the solenoid coil to produce
an actuating magnetic field thereby actuating a mechanical valve,
wherein steps c and d are performed a predetermined number of times
determined through a calibration process and accounts for both
component tolerances and ambient temperature.
20. The method of claim 19, wherein the source current is
insufficient to produce the actuating magnetic field to the actuate
the valve.
21. The method of claim 19, wherein steps c and d are performed
with the second SPST switch open.
22. The method of claim 19, further including the steps of: (e)
after the valve has been actuated, monitoring the source current
through a current sensing element; and (f) once the source current
reaches a predetermined level, repeating steps a and b to recharge
the energy storage device.
23. The method of claim 19, wherein steps a, b, c, d, and e further
comprise: maintaining the first SPST switch closed until the source
current rises to a first predetermined level; opening the first
SPST switch when the source current rises to the first
predetermined level; and closing the first SPST switch once the
source current falls to a second predetermined level.
24. A method comprising the steps of: (a) opening a first single
pole single throw (SPST) switch and closing a second SPST switch,
thereby forward biasing a first diode, allowing a source current to
flow through a capacitor charging the capacitor; (b) opening the
second SPST switch, thereby reverse biasing a second diode and
maintaining the charge of the capacitor; (c) closing the first SPST
switch, thereby allowing the source current to flow through a
solenoid coil; (d) opening the first SPST switch, thereby forward
biasing the second diode and forcing a charge current to flow
through the capacitor utilizing the inductance of the solenoid
coil; (e) repeating steps c and d until the capacitor is
sufficiently charged; (f) upon command, closing both the first and
second SPST switches, thereby reverse biasing both the first and
second diodes and forcing a discharge current to flow from the
capacitor to the solenoid coil causing the solenoid coil to produce
an actuating magnetic field thereby actuating a mechanical valve;
(g) after the valve has been actuated, monitoring the source
current through a current sensing element; and (h) once the source
current reaches a predetermined level, repeating steps a and b to
recharge the energy storage device.
25. The method of claim 24, wherein the source current is
insufficient to produce the actuating magnetic field to the actuate
the valve.
26. The method of claim 24, wherein steps c and d are performed a
predetermined number of times.
27. The method of claim 24, wherein steps c and d are performed
with the second SPST switch open.
28. The method of claim 24, wherein steps a, b, c, d, and e further
comprise: maintaining the first SPST switch closed until the source
current rises to a first predetermined level; opening the first
SPST switch when the source current rises to the first
predetermined level; and closing the first SPST switch once the
source current falls to a second predetermined level.
29. A method comprising the steps of: (a) opening a first single
pole single throw (SPST) switch and closing a second SPST switch,
thereby forward biasing a first diode, allowing a source current to
flow through a capacitor charging the capacitor; (b) opening the
second SPST switch, thereby reverse biasing a second diode and
maintaining the charge of the capacitor; (c) closing the first SPST
switch, thereby allowing the source current to flow through a
solenoid coil; (d) opening the first SPST switch, thereby forward
biasing the second diode and forcing a charge current to flow
through the capacitor utilizing the inductance of the solenoid
coil; (e) repeating steps c and d until the capacitor is
sufficiently charged; (f) upon command, closing both the first and
second SPST switches, thereby reverse biasing both the first and
second diodes and forcing a discharge current to flow from the
capacitor to the solenoid coil causing the solenoid coil to produce
an actuating magnetic field thereby actuating a mechanical valve,
wherein steps a, b, c, d, and e further comprise: maintaining the
first SPST switch closed until the source current rises to a first
predetermined level; opening the first SPST switch when the source
current rises to the first predetermined level; and closing the
first SPST switch once the source current falls to a second
predetermined level.
30. The method of claim 29, wherein the source current is
insufficient to produce the actuating magnetic field to the actuate
the valve.
31. The method of claim 29, wherein steps c and d are performed a
predetermined number of times.
32. The method of claim 29, wherein steps c and d are performed
with the second SPST switch open.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
Not applicable.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
Not applicable.
REFERENCE TO APPENDIX
Not applicable.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The inventions disclosed and taught herein relate generally to
control systems; and more specifically relate to low power control
systems.
2. Description of the Related Art
U.S. Pat. No. 5,532,526 teaches "[a] control circuit for supplying
a load with current having a high-amplitude portion with a rapid
leading edge, and a lower-amplitude portion. The circuit is
input-connected to a low-voltage supply source, and comprises a
number of actuator circuits parallel-connected between the input
terminals and each including a capacitor and a load. Each actuator
circuit also comprises a first controlled switch between the
respective load and a reference line, for enabling energy supply
and storage by the respective load. A second controlled switch is
provided between the capacitor line and the load line, for rapidly
discharging the capacitors into the load selected by the first
switch and recirculating the load current, or for charging the
capacitors with the recirculated load current."
U.S. Pat. No. 6,646,851 teaches "[a] circuit arrangement for
operating a solenoid actuator, for example, an electric motor
provided in the form of a switched reluctance motor, permits
operation of the motor in the event of malfunction or failure of
part of an energy supply. The circuit arrangement advantageously
includes an auxiliary battery serving as a redundance in addition
to a main battery. The auxiliary battery is smaller and has a lower
nominal voltage than the main battery. In order to permit continued
operation of the electric motor in the event of failure, with a
nominal operating voltage which is adapted to the nominal voltage
of the main battery, a capacitor which can be switched on and off
is connected in series to the batteries. An energy quantity can be
accumulated in the capacitor by switching the current switching
through an exciter winding of the electric motor in the manner of a
switching regulator, whereby the nominal voltage of the capacitor
finally exceeds the voltage in the auxiliary battery. When a
sufficient quantity of energy has been accumulated, the electric
motor can be actuated for a short time by means of the energy
accumulated in the capacitor. Electrically actuated braking systems
in commercial vehicles represent a significant and preferred area
of application for the invention."
The inventions disclosed and taught herein are directed to an
improved system and method for controlling a solenoid in low power
applications.
BRIEF SUMMARY OF THE INVENTION
A low power solenoid control circuit including a power source in
series with a sensing element and a first diode, an inductor to
actuate a valve, an energy storage device to store and discharge
energy into the inductor, diodes to control current flow, and
switches and a controller to control the circuit.
The circuit may be operated by closing a first switch, thereby
allowing a source current to flow through an inductor; opening the
first switch, thereby forcing a charge current to flow through an
energy storage device utilizing the inductance of the inductor;
repeating these steps until the energy storage device is
sufficiently charged; and upon command, closing a second switch,
thereby forcing a discharge current to flow from the energy storage
device to the inductor causing the inductor to actuate a mechanical
valve.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
FIG. 1 illustrates a particular embodiment of a low power solenoid
control circuit utilizing certain aspects of the present
inventions.
FIG. 2 is a timing diagram showing certain functionality of the
present inventions.
DETAILED DESCRIPTION
The Figures described above and the written description of specific
structures and functions below are not presented to limit the scope
of what Applicants have invented or the scope of the appended
claims. Rather, the Figures and written description are provided to
teach any person skilled in the art to make and use the inventions
for which patent protection is sought. Those skilled in the art
will appreciate that not all features of a commercial embodiment of
the inventions are described or shown for the sake of clarity and
understanding. Persons of skill in this art will also appreciate
that the development of an actual commercial embodiment
incorporating aspects of the present inventions will require
numerous implementation-specific decisions to achieve the
developer's ultimate goal for the commercial embodiment. Such
implementation-specific decisions may include, and likely are not
limited to, compliance with system-related, business-related,
government-related and other constraints, which may vary by
specific implementation, location and from time to time. While a
developer's efforts might be complex and time-consuming in an
absolute sense, such efforts would be, nevertheless, a routine
undertaking for those of skill this art having benefit of this
disclosure. It must be understood that the inventions disclosed and
taught herein are susceptible to numerous and various modifications
and alternative forms. Lastly, the use of a singular term, such as,
but not limited to, "a," is not intended as limiting of the number
of items. Also, the use of relational terms, such as, but not
limited to, "top," "bottom," "left," "right," "upper," "lower,"
"down," "up," "side," and the like are used in the written
description for clarity in specific reference to the Figures and
are not intended to limit the scope of the invention or the
appended claims.
Particular embodiments of the invention may be described below with
reference to block diagrams and/or operational illustrations of
methods. It will be understood that each block of the block
diagrams and/or operational illustrations, and combinations of
blocks in the block diagrams and/or operational illustrations, can
be implemented by analog and/or digital hardware, and/or computer
program instructions. Such computer program instructions may be
provided to a processor of a general-purpose computer, special
purpose computer, ASIC, and/or other programmable data processing
system. The executed instructions may create structures and
functions for implementing the actions specified in the block
diagrams and/or operational illustrations. In some alternate
implementations, the functions/actions/structures noted in the
figures may occur out of the order noted in the block diagrams
and/or operational illustrations. For example, two operations shown
as occurring in succession, in fact, may be executed substantially
concurrently or the operations may be executed in the reverse
order, depending upon the functionality/acts/structure
involved.
Computer programs for use with or by the embodiments disclosed
herein may be written in an object oriented programming language,
conventional procedural programming language, or lower-level code,
such as assembly language and/or microcode. The program may be
executed entirely on a single processor and/or across multiple
processors, as a stand-alone software package or as part of another
software package.
Applicants have created a low power solenoid control circuit
including a power source in series with a sensing element and a
first diode between nodes, an inductor to actuate a valve, an
energy storage device to store and discharge energy into the
inductor, diodes to control current flow, and switches and a
controller to control the circuit.
The circuit may be operated by closing a first switch, thereby
allowing a source current to flow through an inductor; opening the
first switch, thereby forcing a charge current to flow through an
energy storage device utilizing the inductance of the inductor;
repeating these steps until the energy storage device is
sufficiently charged; and upon command, closing a second switch,
thereby forcing a discharge current to flow from the energy storage
device to the inductor causing the inductor to actuate a mechanical
valve.
FIG. 1 is an illustration of a first preferred embodiment of a low
power solenoid control circuit 10 showing certain aspects of the
present inventions. The circuit 10 is preferably incorporated into
a solenoid valve of the type commonly used in connection with
pneumatic and/or hydraulic industrial control systems. The circuit
10 preferably incorporates a three wire connection to an external
supervisory control system, such as a distributed control system
(DCS) or a programmable logic controller (PLC). The three wire
connection preferably includes a power connection and a control
connection, both referenced to a ground or neutral connection. The
power connection is preferably a direct current (DC) voltage of
approximately twelve or twenty-four volts. Other voltages may be
accommodated, depending on actual implementation. The control
connection may be incorporated into the power connection, thereby
requiring only a two wire connection to the supervisory control
system.
The circuit 10 preferably includes a power source 12. The power
source 12 is preferably DC as provided through the two or three
wire connection. The power source 12 may be independent of the two
or three wire connection or may simply be embodied by the two or
three wire connection.
The circuit 10 also preferably includes a sensing element 14 in
series with the power source 12. In one embodiment, the sensing
element 14 is a precision shunt resistor through which current can
be calculated by measuring voltage across the shunt. However, the
sensing element 14 may take other forms, such as an inductive
current sensor, a hall-effect current sensor, another current
sensing device, a voltage sensing device, or a power sensing
device. The sensing element 14 may also be incorporated into other
components of the circuit 10. The sensing element 14 is implemented
to sense or otherwise measure the current or power being delivered
through the power source 12.
In any case, the circuit 10 preferably includes a controller 16
that monitors the sensing element 14. The controller 16 preferably
comprises a programmable microcontroller, such as the Microchip
PIC16F631. However, the controller 16 may alternatively be
implemented in hardwired logic. In any case, the controller 16
preferably monitors the sensing element 14 in order to determine
the current, voltage, and/or power applied thereto. The controller
16 then manipulates or otherwise operates other components of the
circuit 10 based at least in part on the input from the sensing
element 14, as will be discussed in greater detail below.
The circuit 10 also preferably includes a first diode 18 in series
with the power source 12 and the sensing element 14. The first
diode 18 is preferably rated to accommodate and protect the power
source 12. For example, when forward biased, the first diode 18 is
preferably rated to pass the current the power source 12 is
expected to provide under normal and acceptable abnormal
conditions. When reverse biased, the first diode 18 is preferably
rated to block any expected discharge current, which will be
discussed in greater detail below. Where the controller 16 is more
capable, the first diode 18 can be replaced by a switch controlled
by the controller 16. For example, the controller 16 may monitor
both current amplitude and direction through the sensing element 14
and open a switch used in place of the first diode 18, when the
first diode 18 would normally be reverse biased or otherwise
prevent current flow.
The circuit 10 also preferably includes a solenoid coil 20, or some
other inductor. In the preferred embodiment, the coil 20 is
operable to actuate a mechanical valve, such as a pneumatic and/or
hydraulic control valve. The mechanical valve then preferably
manipulates or otherwise controls a process control valve. However,
in some implementations, the coil 20 may be configured to actuate
the process control valve directly.
The inductor, or coil, 20 produces a magnetic field, which is
proportional to the current that flows therethrough. The field is
used to linearly displace a plunger, or other mechanical element,
in order to actuate the valve. One will appreciate that the field
must be of sufficient strength, in order to move the plunger and
thereby actuate the valve. One with ordinary skill in the art will
appreciate that there are a number of ways to increase the field
strength for a given current. For example, one may choose to
increase the turn density of the coil 20. However, there are often
practical limitations, especially in certain low power
applications, such that the available current is simply
insufficient to produce a strong enough field to actuate the
valve.
Therefore, the circuit 10 of the present inventions preferably
include an energy storage device 22, such as a capacitor, to
accumulate energy from the available current and discharge that
stored energy into the coil 20. Because this discharge current can
be significantly greater than a source current, from which it was
created, a controlled discharge is capable of creating a sufficient
field to actuate the valve. The capacitor 22 can be charged
directly from the source current, produced by the power source 12.
However, because the discharge current is expected to need to be
greater than the source current, in order to actuate the valve, the
energy storage device 22 is also preferably operable to be charged
by a charge current induced by the inductor 20, as will be
discussed in greater detail below.
In order to prevent premature discharge of the energy storage
device 22, the circuit 10 preferably includes a second diode 24
configured to retain the charge on the capacitor 22. The second
diode 24 is preferably rated to pass the source current, when
forward biased, and block the energy stored in the energy storage
device 22, when reverse biased. As with the first diode 18, the
second diode 24 may be replaced with a switch controlled by the
controller 16. However, this may require the controller 16 to have
additional inputs and/or be more predictive in operation, in order
to control the charge on the capacitor 22.
To control the source current, the charge current, and the
discharge current, as well as other aspects of the inventions, the
circuit 10 also preferably includes first and second switches
26,28. The first and second switches 26,28 are preferably single
pole single throw (SPST) switches. The first and second switches
26,28 may be mechanical switches or may be solid state devices,
such as transistors or more specifically MOSFETs. For example, the
first switch 26 and/or the second switch 28 may be a normally
closed depletion mode MOSFET, or similar device.
The first and second switches 26,28 are preferably controlled by
the controller 16, as will be discussed in more detail below. For
example, the first switch 26 is preferably primarily used to
control the source current in such a way as to induce the charge
current using the inductor 20. The second switch 28 is preferably
primarily used to control the discharge current into the coil 20,
thereby actuating the valve on command from the supervisory control
system.
The circuit 10 may also include a current limiting device 30, such
as a limiting resistor, in series with the power source 12 to
further protect the components of the circuit 10. Alternatively,
the current limiting device 30 may be incorporated into other
components of the circuit 10. For example, the shunt resistor 14
may be sized to serve both as the sensing element 14 and the
current limiting device 30.
Other and further embodiments utilizing one or more aspects of the
inventions described above can be devised without departing from
the spirit of Applicant's invention. For example, as discussed
above, the diodes 18,24 may be replaced with controlled switches,
which may be embodied by transistors, such as MOSFETs. Further, the
various methods and embodiments of the present invention can be
included in combination with each other to produce variations of
the disclosed methods and embodiments. Additionally, the
embodiments described above may be improved and/or further
enhanced. In some instances, discussion of singular elements can
include plural elements and vice-versa. However, the embodiment
described above is preferable in that the minimal components
described work together to reduce size, cost, and manufacturing
complexity.
Now referring additionally to FIG. 2, in use, the circuit 10
successively charges the energy storage device 22 until sufficient
energy is stored therein. Upon command, the energy stored in the
energy storage device 22 is discharged into the inductor 20 thereby
generating a magnetic field sufficient to actuate the valve. It can
be seen that the source current is otherwise insufficient to
generate a sufficient magnetic field without the teachings of the
present invention.
In more detail, let us begin by assuming that the capacitor 22 has
been fully discharged and therefore no longer stores significant
energy and that both switches 26,28 are open, as shown in FIG. 1.
The first switch 26 is closed at time T1, thereby allowing the
supply current to flow through the coil 20. When the supply current
reaches a first predetermined level, at T2, the first switch 26 is
opened. The inductor 20 therefore forces the supply current to
forward bias the second diode 24 inducing the charge current
through the capacitor 22. When the supply current subsides to a
second predetermined level, at T3, the first switch 26 is closed
again, and the cycle is repeated. When the first switch 26 is
closed, the second diode 24 is reversed biased, thereby preventing
the capacitor 22 from discharging. Therefore, each time the cycle
is repeated, the energy in the capacitor 22 increases.
As shown in FIG. 2, the cycles may be initiated with the capacitor
22 fully discharged. Alternatively, the capacitor 22 may be
directly from the supply current by temporarily closing the second
switch 28. This would start the stored energy level at the point
shown at T3, versus T1.
During manufacturing of the solenoid valve, of which the circuit 10
is preferably a part, the number of charging cycles that are
required can be determined. More specifically, due to variances in
the components of the circuit 10 and/or other variables, such as
ambient operating temperature, it is expected that a different
number of cycles may be required for different circuits 10 and/or
different valves before the energy storage device 22 has
accumulated sufficient energy to reliably actuate the valve.
Therefore, once the circuit 10 is assembled, a calibration process
can be conducted to determine how many cycles will be required for
a given implementation. The necessary number of cycles is
preferably programmed, or otherwise configured, into the controller
16. In the example shown in FIG. 2, this predetermined number of
cycles is three. Therefore, at T7, the energy storage device 22 has
stored sufficient energy to induce sufficient magnetic field in the
inductor 20, in order to actuate the valve.
At this point, the energy storage device 22 is fully charged and
ready to supply a discharge current to the inductor 20, and thereby
actuate the valve. The controller 16 may maintain the first switch
26 in the open position. One advantage of this approach is an
energy savings in low power applications, and is especially helpful
where the valve is infrequently actuated. Alternatively, the
controller 16 may close the first switch 26, thereby allowing the
supply current flow through the inductor 20. One advantage of this
approach is that there is some field already present in the
inductor 20, when the energy storage device 22 discharges.
At T8, the controller 16 receives a control input, through the
control connection from the external supervisory control system.
The controller 16 immediately closes both switches 26,28, thereby
releasing the energy stored in the energy storage device 22. This
discharge current from the capacitor 22 reverse biases both diodes
18,24 and flows through the inductor 20. The surge of energy causes
the coil 20 to generate a magnetic field sufficient to actuate the
valve.
It can be seen that as we approach T9, the energy stored in the
capacitor 22 is dissipated. Once the voltage associated with that
energy falls below the supply voltage, of the power supply 12, the
first diode 18 becomes forward biased, thereby allowing the supply
current to begin building once again. When the controller 16 begins
to detect the supply current rising, the controller preferably
opens the second switch 28.
At this point, the controller 16 may begin the cycles of opening
and closing the first switch 26, as discussed above, to recharge
the capacitor 22. This will ensure the energy storage device 22 is
capable of re-actuating the valve, if that should be necessary.
This may prove especially advantageous where the valve is
frequently actuated and/or where the valve is susceptible to
inadvertently dropping out.
It is possible for the relatively high discharge current to induce
so much energy in the inductor 20, that the power supply 12 could
become overloaded. In order to prevent such an overload, the
controller 16 may leave the second switch 28 closed and begin
cycling the first switch 26 instead. More specifically, after
closing both switches 26,28 and thereby discharging the capacitor
22, the controller 16 may open the first switch 26 when the sensed
current through the sensing element 14 begins to approach the power
supply's 12 current limit. The controller 16 preferably waits a
predetermined fixed time, allowing the current to fall off, before
closing the first switch 26 again. This fixed time may be
calculated based on the resistance, inductance, and/or capacitance
of the circuit 10 or may be determined during the calibration
process. This cycle can be repeated until the energy in the
inductor 20 is bled off and/or the capacitor 22 is recharged.
This allows the controller 16 to function as a current regulator by
controlling the duty cycle of the first switch 26 based on input
from the sensing element 14. Such functionality may allow higher
currents through the coil 20, as may be desirable in certain
applications.
The controller 16 may be more advanced that that described above.
For example, the controller 16 may control and/or measure the
source current waveform shown in FIG. 2. From this, the controller
16 may infer the voltage applied to the circuit 10 by the power
supply 12, based in part on the switching times of the switches
26,28.
Furthermore, it can be appreciated that the plunger of the solenoid
valve may be subject to mechanical shock. In the valve has been
actuated, and is subject to mechanical shock, such shock may cause
the valve to drop out, inadvertently closing and/or opening the
valve depending on the valve construction. However, as the plunger
moves with respect to the coil 20, it will likely induce a current
spike in the inductor 20. This spike may be reflected in the source
current waveform monitored by the controller 16. Any such pattern
could be observed and stored within the controller 16. This could
be recorded as part of the calibration process discussed above.
Thereafter, the controller 16 may continuously, or periodically,
compare the source current to this pre-observed pattern, in order
to detect when and if the solenoid valve has dropped out, or
inadvertently actuated. If the controller 16 detects an inadvertent
drop out or actuation, the controller 16 may take immediate
corrective measures, without waiting for input from the external
supervisory control system. For example, if the controller 16 has
actuated the valve and detects an inadvertent drop out, the
controller 16 may immediately re-actuate the valve.
Alternatively, or additionally, the controller 16 may inform the
supervisory control system, through a two-way communications link,
or operator, by sounding an alarm. This may be accomplished using a
separate output or by overriding the control input. This would
allow the supervisory control system or operator to take corrective
or preventative measures, as needed. The controller 16, or
supervisory control system, may also log such occurrences and
thereby determine if the solenoid valve needs to be replaced and/or
if the power supply 12 is inadequate.
In some implementations, the order of steps can occur in a variety
of sequences, unless otherwise specifically limited. The various
steps described herein can be combined with other steps,
interlineated with the stated steps, and/or split into multiple
steps. Similarly, elements have been described functionally and can
be embodied as separate components or can be combined into
components having multiple functions.
The inventions have been described in the context of preferred and
other embodiments and not every embodiment of the invention has
been described. Obvious modifications and alterations to the
described embodiments are available to those of ordinary skill in
the art. The disclosed and undisclosed embodiments are not intended
to limit or restrict the scope or applicability of the invention
conceived of by the Applicants, but rather, in conformity with the
patent laws, Applicants intend to fully protect all such
modifications and improvements that come within the scope or range
of equivalent of the following claims.
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